The present invention relates to a system for transmitting video, voice and control signals on a multiplex bi-directional transmission basis in both directions at the same time between two video appliances, e.g., between a television camera (which will be referred merely as the camera, hereinafter) and a unit for controlling the camera, i.e., camera control unit (CCU) (which unit will be referred merely as the CCU, hereinafter).
When it is desired to connect the camera to the CCU to attain multiplex bi-directional transmission of video, voice and control signals therebetween for example, it has been conventionally well known to use a triplex coaxial cable (which will be referred to as the cable, hereinafter) called TRIAX cable to transmit these signals on a frequency division multiplex communication basis. An example of the above system is shown in FIG. 1, in which 3 sorts of video signals R, G and B and 4 sorts of voice signals A1, A2, A3 and A4 generated at a camera 100 are transmitted from the camera 100 to a CCU 200, while a monitoring video signal M generated at the CCU 200, a voice signal A5, a control signal D for controlling the operation of the camera 100 and so on are transmitted from the CCU 200 to the camera 100.
In order to transmit a plurality of signals in two ways through a single transmission line or cable 7, different frequency bands are assigned respectively exclusively to these signals so that the carriers of the signals having the different frequency bands are subjected to amplitude modification (AM), as shown in FIG. 2. This results in that, due to the provision of a filter in the camera 100 or CCU 200, these signals appearing on the cable 7 at the same time can be separated from each other on the side of the camera 100 or CCU 200 without interfering with each other at their all components.